It is known that the retinal reflectivity of an eyeball is different for each eyeball and may be used for identification purposes, similar to fingerprints. Generally, a retinal identifier is a relatively large and complicated device requiring a large memory and apparatus (a computer or the like) for comparing the retinal reflectivity information to stored information. Because of the size and power requirements, retinal identifiers can only be used in very limited applications where size, power, etc. are not a factor to be considered.